The film, which stars Eisenberg as a young man trying to make his way in 1930s Hollywood with the reluctant help of his name-dropping uncle, includes a line calling Hollywood "boring, nasty and dog-eat-dog".

When asked how closely that described her own experience as the world's "gnarliest popularity contest", she joked it was like high school for adults.

"Most people want to entertain people and make a bunch of money. It's not a bad thing, but if it also doesn't hold hands with a genuine desire [to tell a story as art] then that sucks," she said.

"That's pretty rampant. Human beings are always clawing each other to get on top, and that's is most industries. Hollywood can have a surface nature that makes it more obvious."

In his first public appearance in Cannes this year, Allen, who is opening the festival for the third time, was also compelled to defend his record of making films with older men romancing much younger women.

His latest storyline sees Kristen Stewart, 26, involved with a boyfriend more than twice her age in a theme fans of his work will be familiar with.

Calling himself a "romantic", he was challenged on whether he would ever make a film featuring an older woman and her much younger lover.

"I wouldn't hesitate to do that if I had a good idea for a story with a 50-year-old woman and a 30-year-old man," he said.